假设我在名为wx_data的表中有以下数据(温度与此处列出的日期和城市不准确)city,wx_date,avg_tempKansasCity,2012-11-01,28KansasCity,2012-11-02,42KansasCity,2012-11-03,86KansasCity,2012-11-04,39KansasCity,2012-11-05,27KansasCity,2012-11-06,65KansasCity,2012-11-07,62KansasCity,2012-11-08,55KansasCity,2012-11-09,95KansasCity,2012-11-1